1. Field of the Invention
This invention relates to a lock construction providing improved security features. More particularly, this invention relates to a lock assembly having a decreased vulnerability to intrusive physical attack.
2. Background of the Invention
Because the security of conventional locks and padlocks can be violated in many different ways, it is often desirable to afford increased security in such mechanisms. A conventional lock cylinder assembly is known to include a security harness of sturdy construction that is designed to enshroud the exterior of the lock mechanism to protect the interchangeable core from destructive physical attack.
Other security features are aimed at protecting the lock core from attack. In particular, improved security features are taught in U.S. Pat. No. 4,918,950 to Foshee; U.S. Pat. No. 4,180,996 to Lebrecht; and U.S. Pat. No. 4,949,564 to Barzilai. Foshee teaches a complicated cylinder cap and keyway-disc mechanism to protect the lock core from attack. To protect the lock core, the device disclosed in the Foshee patent requires many parts, as well as a complicated assembly procedure, which causes the lock's manufacturing costs to be high. Another disadvantage of the device disclosed in the Foshee patent is the complexity of the cap which protects the lock core. Furthermore, the device of the Foshee patent is inaccessible when the padlock is in its locked position.
Lebrecht teaches a device which protects against a potential thief sawing through a padlock's protective casing by implanting freely rotatable hardened pins within the padlock shrouding which spin when attacked by a saw blade. However, the device disclosed in the Lebrecht patent has the disadvantage of not protecting the front face of the interchangeable lock core from attack by an intruder. The lock core disclosed in the Lebrecht patent is readily accessible by a conventional pulling tool.
Barzilai teaches a lock core cover which slidably fits within the end of a tubular padlock. However, the cover shown in the Barzilai patent is vulnerable to attack. The Barzilai cover is held in place by a relatively weak and expensive-to-manufacture snap-action fastener pin.
Thus, a need exists for a simple, inexpensive device to protect a padlock's lock core from attack by would-be thieves. In particular, a need exists for a padlock which protects the padlock core from being pulled from the padlock shroud by means of a "slam-puller," "nose-puller" or other lock attacking tool. Such tools are used to attack the relatively soft padlock core, and thereby, to breach the security of the padlock. A further need exists to accomplish this feature using a simple construction having few parts.
In summary, known means of increasing the security of lock mechanisms have the disadvantage of increasing the overall complexity of the mechanism and increasing manufacturing costs and the number of parts necessary to achieve increased security. A substantial need exists for an efficiently designed, economical, high security lock system.